Someone else in my office showed me the path to the option and it showed up on theirs but was not on mine so I wasn't sure how to turn it off / on as it wasn't not even showing up there. Their path was View, Show / Hide, Toolbar Items, Show Select & Zoom tools, and that is where the + / - sign was showing up for them but not for me. So if this is the same problem your having, hover around the bottom tool bar.